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Re: Scalars and Matrices:
From: |
Francesco Potorti` |
Subject: |
Re: Scalars and Matrices: |
Date: |
Fri, 15 Oct 1999 13:56:35 +0200 (CEST) |
(Ted Harding) <address@hidden> writes:
> Sorry, I don't think I can sympathise with this. As a general convention
> for associativity,
>
> A*B*C = (A*B)*C
Johan Kullstam <address@hidden> writes:
no. associativity says, by definition, that
(A*B)*C = A*(B*C) (A)
What Ted means (I suppose) is that, in a programming language, when
dealing with non-associative binary operators (like the product for
matrices), there is a commonly used default assumption, unless otherwise
stated in the language definition.
This assumption is that the language's operator is "left-associative",
that is, grouping is done from left to right.
This is quite common and, in my opinion, intuitive. I think Octave
should not change anything in the way it deals with these ambiguities.
This is what the Octave manual says about this issue:
When operators of equal precedence are used together, the leftmost
operator groups first, except for the assignment and exponentiation
operators, which group in the opposite order. Thus, the expression `a
- b + c' groups as `(a - b) + c', but the expression `a = b = c' groups
as `a = (b = c)'.
Possibly, if someone thinks so, some text could be added to the Octave
manual which clarifies this issue further. If John Eaton does not feel
like adding that text himself, I am sure he will be glad to accept
reasonable contributions.
--
Francesco PotortÃ¬ (researcher) Voice: +39-050-593 203 (op. 211)
Computer Networks Group Fax: +39-050-904052
CNUCE-CNR, Via Santa Maria 36 Email: address@hidden
56126 Pisa - Italy Web: http://fly.cnuce.cnr.it/
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- Re: FW: Scalars and Matrices:, (continued)